This invention relates to so-called slip form pavers having dowel bar inserters. More particularly, this disclosure sets for a chain feeder for a dowel bar inserter, which is contained within the transport profile of the slip form paver. This containment within the transport profile enables the dowel bar feeder to cycle once insertion has commenced and does not require unnecessary bolster extension.
Concrete slipform pavers are known. Specifically, such pavers include a xe2x80x9ctractorxe2x80x9d and a xe2x80x9cpaving kitxe2x80x9d.
Regarding the tractor, most concrete slipform pavers include a tractor, which is comprised of a rectilinear frame. This rectilinear frame has bolsters extending parallel to the direction of machine travel and cross beams extending across the paved roadway. The rectilinear frame thus straddles the concrete roadway or runway while it is paved. This frame is propelled and supported on either end by side crawler track(s). The frame supports a diesel engine driven hydraulic power unit, which supplies power to the tractor and paving kit.
The paving kit is typically suspended below the rectilinear tractor frame by mechanical means. The paving kit takes its hydraulic power from the power unit on the tractor. The tractor and paving kit comprise the slipform. This slipform passes over concrete placed in its path. The concrete is placed in a relatively even and level mass that can be conveniently paved. During this slipform process the tractor attached paving kit spreads the concrete dumped in the path of the paver, levels and vibrates it into a semi-liquid state, then confines and finishes the concrete into a slab with an upwardly exposed and finished surface. Sideforms mounted to the side of the slipform kit confine the sides of the slab during the paving process.
The tractor typically has either two or four crawler tracks supporting and propelling the frame and attached paving kit. Other kits can be attached to these tractors such as kits for conveying and spreading concrete and trimming and spreading base materials. For the purposes of this description, we will focus on the paving kit working in conjunction with a rear mounted, dowel bar inserter kit used for slipforming a concrete slab and concurrently inserting dowel bars in the plastic concrete across the slipform paved slab.
Dowel bar and tie bar inserters for such paving machines are known. Dowel bars are placed parallel to the direction of machine travel and ties bars are placed across the direction of machine travel. Specifically, three types of inserters for such bars are known. First, there is the tie bar inserter for the edge of the slab. This tie bar is placed transverse to the paving direction and enables tying of sequentially placed side-by-side slabs, one to another. This type of tie bar and tie bar inserter is not of concern here.
Second, there is the tie bar inserter for placing tie bars completely within the placed slab. A placed slab might be a two or more 12xe2x80x2 (3.657 mm) wide lane being placed concurrently in one pass. These tie bars are placed in a line transverse to the direction of machine travel. These tie bars enable a joint to be subsequently cut in the middle of the slab parallel to the direction of machine travel. Expansion of the slab across the dimension of machine travel is permitted. This type of tie bar and dowel bar inserter is not of concern here.
Finally, and the most difficult insertion problem is the dowel bar inserter for placing dowel bars parallel to the direction of machine travel. The dowel bars are simultaneously placed in a line (or row) on what are typically 12xe2x80x3 (305 mm) centers, across the entire slab being slipformed by the paver. These dowel bars enable a joint to be subsequently cut in the slab across the direction of machine travel. The dowels provide load transfer between the adjoining panels in the direction of machine travel.
This type of dowel bar inserter presents the most difficult insertion problem in any slipform paver. Additionally, this type of dowel bar inserter requires modification to be made to the slipform paver to attach the dowel bar inserter. In addition to this, great effort is required to attach or remove the dowel bar inserter from the slipform paver. It might take an additional two days to assemble a machine with a dowel bar inserter. This great effort has limited the dowel bar inserter""s acceptance on smaller paving jobs. In what follows, we first discuss the most modern pavers, which have been developed. Second, we turn to the prior art problem of dowel bar insertion. Third, we set forth the mechanical problem of attachment and removal of dowel bar inserters to known pavers, including the pavers summarized above.
In Guntert et al U.S. Pat. No. 5,590,977 issued Jan. 7, 1997 entitled Four Track Paving Machine and Process of Transport we have disclosed a portable slip form paver that used telescoping members in the direction of machine travel. A four track paver is disclosed having a frame which telescopes for transport to reduce the dimension of the machine in the direction of paving machine travel. A rectilinear tractor frame is provided. The frame includes four crawler tracks, one connected to each corner of the frame via a side bolster. The crawler tracks are directly supported on a hydraulic cylinder and mounted for pivotal movement about the vertical axis of the hydraulic cylinder. The frame telescopes at side bolsters between the leading and trailing crawler tracks at the sides of the machine. When expanded, the paving machine has the full dimension required for paving. When contracted, the paving machine has a profile allowing convenient transport. Most importantly, such expansion and contraction of the machine in the direction of paving travel does not require substantial paver or paver kit disassembly. As a consequence, a convenient method of loading and off loading to a hauling flatbed trailer exists. With the frame contracted at the side bolsters and the tracks pivoted parallel to the pavement spanning dimension of the frame, both frame and paving kit are elevated and a transporting flatbed trailer moved under the paver. Supports are installed to relieve the slipform paving kit from the full weight of the tractor frame, and the tracks lifted. There results a four track paver profile transportable within a maximum width envelope which can be legally transported on the highway without a pilot car (in the U.S.A. this is this is 12xe2x80x2 or (3.657 M.) This patent is incorporated by reference to this disclosure as if set forth in full.
In Guntert et al U.S. Pat. No. 5,615,972 issued Apr. 1, 1997 entitled Paving Machine with Extended Telescoping Members (see also U.S. Pat. No. 5,647,688) we have disclosed a portable slip form paver having an extendable width. A conventional telescoping frame on a paving tractor is provided with fixed frame cross beam extension members for insertion to and attachment with a telescoping frame member. The conventional telescoping frame includes paired forward and paired rear side-by-side female tube members. Each forward and rear tube member conventionally acts for the telescoping support of male extension members which attach directly to the side bolster, which in turn attaches to the hydraulic jacking columns and crawlers. Within the limits of expansion, the male extension members co-acting with clamps acting through the female tube members provide for both movement of the point of crawler support and expansion of the paving width of the tractor frame. Into this combination, extenders are added for attachment to the supported end of the male extension members interior of the female telescoping members. During frame width expansion, the male telescoping members are expanded to register their ends interior of the female telescoping members to attachment access ports in the female telescoping member. The extenders are inserted, supported, and registered at complimentary attachment apertures with attachment to the male telescoping members taking place. Once attachment has occurred, further extension of the male telescoping members occurs. A simple system of pinned cross bracing reinforces the extended frame with relatively light bracing members. When the telescoping members at both sides of the frame are provided with the extenders to extend the telescoping span of the paver, a tractor of greater expansion and range of expansion capability is provided. This width expansion obviates the need for fixed frame extensions, and permits frame expansion without heavy lifting equipment. This patent is incorporated by reference to this disclosure as if set forth in full.
Machines built to the specification of the above referenced patents require dowel bar inserters from time to time. Regarding such dowel bar insertion, the dowel bars must be placed parallel to the direction of machine travel. A line of dowel bars must be simultaneously inserted across the slab being formed. Typically, 12 to 34 or more such dowel bars can be inserted depending upon the width of pavement being paved. Center to center spacing of insertion between the dowel bars can vary. Variation can occur from about 12 inches (305 mm) on typical highway paving up to 18 inches (457 mm) for certain airport runways, aprons and taxiways. All such dowel bars must be inserted simultaneously by a mechanism, which remains is stationary with respect to the plastic concrete slab being continuously formed. Thus, the dowel bar inserter must be on rails, which permit dowel bar inserter travel in the direction of concrete placement by the machine.
Dowel bars are placed at relatively short intervals along the direction of machine travelxe2x80x94in the order of every 15 feet (4.57 M) of machine travel. Slipform pavers operate at speeds up to 15 feet per minute or more at times. It must be remembered that the individual dowel bars must be separately loaded at each insertion station between dowel bar insertions. In the prior art, such loading has occurred by a cart traveling across the empty dowel bar insertion stations located directly over a dowel bar inserter confining pan, which slides a top a recently formed slab. This cart has produced at least four difficulties in the past.
First, the cart may contains stacked bars or at least bars rolling against each other. As the stacked (or touching) bars are pulled across empty dowel bar insertion stations, the individual dowel bars drop into the stations. This dropping is not always uniform because of the contact between bars. For example, it is known to have one end of the bar drop from the car with the other end of the bar remaining in the cart. When such partial dropping of the bar occurs, the cart is jammed in its path of travel across the slab. Paving must stop until such jams are cleared.
Second, the cart must first distribute all the bars across the slab at a first and a lower speed (to prevent jamming) and then return to the loading side of the machine at a speed before insertion of the dowel bars into the slab can occur. Once the cart is out of the way of the insertion forks at the side of the paver, dowel bar insertion can occur with the inserters remaining stationary with respect to the slab. While the cart is in the process of returning from its distribution of dowel bars, no insertion of the distributed bars can occur.
Third, the cart protrudes from the side of the paver as the first insertion fork can be located as close as 6xe2x80x3 (15 cm) from the edge of pavement. Such protrusion must not interfere with the tracks. This being the case, the length of the bolster between tracks must be increased to accommodate that extra spatial interval required by the cart or the entire crawler track must be moved away from edge of pavement so the cart can clear the track. Furthermore, the protrusion of the cart and track for the cart from the side of the paver constitutes an obstruction to the side of the paver. Articles, such as fire hydrants or street light poles, close to the paving path of the paver must be removed. Such removal increases paving time and expense.
Fourth, the width of the cartxe2x80x94exceeding the length of the dowel barsxe2x80x94must be added to the path traveled by the dowel bar inserters during the required placement of the dowel bars to the slab. This means that the length of the dowel bar inserter in the direction of machine travel must be increased. Taking the case of a four track paver, the distance of the bolster extending in the direction of machine travel must be increased.
Placement of dowel bar inserters on existing pavers has also caused difficulty. To place such inserters on a conventional paver, substantial machine disassembly and modification must occur. First, the trailing finishing pan must be removed. Second, the conventional bolsters must be modified and extensions added to allow room in front of the rear crawler track to make room for the dowel bar inserter to work. These bolster extensions also support the dowel bar inserter kit. Third, because the rear crawler tracks have been moved back, a cross beam must be added between the rear bolsters to prevent the extended bolsters from twisting under load. Fourth, an optional spreader plow for the correcting beam must be added. Fifth, a correcting beamxe2x80x94the beam that establishes the final slab grade from the paver, after the dowel bar inserter inserts the barsxe2x80x94must be added. Thereafter, the trailing finishing pan is reattached behind the correcting beam. To fit these required pieces of the dowel bar inserter between the rear of the slipform conforming pan and ahead of the rear crawler track can increase the center to center distance between the front and rear crawler tracks by 20xe2x80x2 (6.10 M). The dowel bar inserter and its related attachments also necessitates two additional trucks to haul it.
This process of attachment of dowel bar inserters is sufficiently complex, that for relatively small paving jobs, dowel bar inserters are not used. Instead, such dowel bars are tied together and support on xe2x80x9cbasketsxe2x80x9d or xe2x80x9cchairsxe2x80x9d and secured to the subgrade ahead of the slipform. The baskets hold the dowels in position at the center of the slab. Although, these dowel baskets assemblies are significantly more expensive than loose dowels and require significant labor to install the extra mobilization and transport cost of paver with a dowel bar inserter outweighs this extra cost on a small job.
In combination with a slipform paver, a new chain feeder is disclosed which is contained within the profile of a slipform paver and enables improved cycling time for the insertion of dowel bars. The chain feeder is used in combination with a plurality of dowel bar inserter stations. Each dowel bar insertion station includes an upper dowel bar shuttle with an upper shuttle bar opening for receiving a dowel bar and a lower dowel bar shuttle with a lower shuttle bar opening for permitting a dowel bar to fall through the lower dowel bar shuttle. A dowel bar inserter pan supports the lower dowel bar shuttle and defines a pan opening for permitting dowel bars inserted to the lower dowel bar shuttle to fall through the pan opening. A single file dowel bar path is provided immediately above the plurality of dowel bar inserter stations overlying the upper dowel bar shuttle for each inserter station. The feeder includes a plurality of feeding lugs for pushing dowel bars along the single file dowel bar path parallel to openings in the upper dowel bar shuttle. This enables dowel bars to fall into the upper dowel bar shuttle when the upper dowel bar shuttle is empty and to pass over the upper dowel bar shuttle at the upper shuttle bar opening when the upper shuttle bar opening is filled with a dowel bar. The feeder includes a plurality of feeding lugs along the single file dowel bar path to load the upper dowel bar shuttle successively with dowel bars for insertion to a slab formed under the dowel bar inserter pan. When the dowel bars are fully inserted, the upper dowel bar shuttle moves relative to the lower dowel bar shuttle. This permits the upper shuttle bar opening in the upper dowel bar shuttle and the lower shuttle bar opening in the lower dowel bar shuttle to move into registration one with another. Dowel bars fall from the upper shuttle bar opening in the upper dowel bar shuttle into the lower shuttle bar opening of the lower dowel bar shuttle through the pan opening in the dowel bar inserter pan and on to a slab formed beneath the dowel bar inserter pan. Thereafter, the dowel bar inserters place the dowel bars centrally of the recently slipformed slab.